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Background: From July to September 1994, 29 cases of community-acquired Legionnaires' disease (LD) were reported in Delaware. The authors conducted an investigation to a) identify the source of the outbreak and risk factors for developing Legionella pneumophila serogroup 1 (Lp-1) pneumonia and b) evaluate the risk associated with the components of cumulative exposure to the source (i.e. distance from the source, frequency of exposure, and duration of exposure)., Methods: A case-control study matched 21 patients to three controls per case by known risk factors for acquiring LD. Controls were selected from patients who attended the same clinic as the respective case-patients. Water samples taken at the hospital, from eight nearby cooling towers, and from four of the patient's homes were cultured for Legionella. Isolates were subtyped using monoclonal antibody (Mab) analysis and arbitrarily primed polymerase chain reaction (AP-PCR)., Results: Eleven (52%) of 21 case-patients worked at or visited the hospital compared with 17 (27%) of 63 controls (OR 5.0, 95% CI : 1.1-29). For those who lived, worked, or visited within 4 square miles of the hospital, the risk of illness decreased by 20% for each 0.10 mile from the hospital; it increased by 80% for each visit to the hospital; and it increased by 8% for each hour spent within 0.125 miles of the hospital. Lp-1 was isolated from three patients and both hospital cooling towers. Based on laboratory results no other samples contained Lp-1. The clinical and main-tower isolates all demonstrated Mab pattern 1,2,5,6. AP-PCR matched the main-tower samples with those from two case-patients., Conclusion: The results of our investigation suggested that the hospital cooling towers were the source of a community outbreak of LD. Increasing proximity to and frequency of exposure to the towers increased the risk of LD. New guidelines for cooling tower maintenance are needed. Knowing the location of cooling towers could facilitate maintenance inspections and outbreak investigations.

In two women aged 65 and 49 years and a man aged 64 years, severe respiratory failure developed and a pulmonary disease was suspected. They also had a minor systolic murmur. At further investigation no pulmonary cause for the disease could be established. Pulmonary artery catheterization revealed increased pulmonary artery and wedge pressures and transthoracic and transoesophageal echocardiography revealed mitral valve insufficiency. Two patients had valve surgery, the third received medication. Respiratory failure is a common problem in an intensive care unit. If this condition is caused by mitral valve insufficiency the clinical picture is not always that of acute left ventricular failure with hydrostatic pulmonary oedema due to backward failure. In patients with respiratory failure due to mitral valve pathology initial diagnostic problems may be overcome by combining the findings of pulmonary artery catheterization and transthoracic and transoesophageal echocardiography.

We investigated an outbreak of fever, most likely due to a contaminated whirlpool, among nine adults and six children residing in a summerhouse. The outbreak was characterized by a high attack rate, short incubation periods, influenza-like symptoms, and rapid recoveries, all features typical of Pontiac fever. However, the children had less-characteristic symptoms than the adults, and they did not have any sequelae. Findings on the children's chest radiographs were unremarkable, and none of the children had leukocytosis. Evidence of Legionella pneumophila infection was found in six cases: in one case by isolation of L. pneumophila serogroup 1 and detection of legionellae by PCR, and in five cases by seroconversion to the clinical isolate. Six additional cases had presumptive evidence of legionella infection, with seroconversion to Legionella micdadei antigen; a PCR assay was also positive for legionellae for one of these cases. In contrast, two adult nonusers of the whirlpool had no symptoms and no serological evidence of infection. Serological testing and cultures for other pathogens, as well as cultures of all environmental samples, were negative. This investigation demonstrates the differences between adults and children with respect to the clinical picture of Pontiac fever; furthermore, it shows that culture and PCR assay of tracheal aspirates for legionellae can be performed in a hospital setting for rapid diagnosis, although the sensitivities of these methods are low.

Patients with defective immune systems are susceptible to Legionella infection, especially when the defect involves cell-mediated immunity. Thus, acquired immune deficiency syndrome (AIDS), corticosteroid administration, and hairy cell leukemia are risk factors for Legionellosis. Patients who have AIDS may be at risk for relapsing infections. Corticosteroid administration appears to predispose patients to simultaneous infection with multiple strains of Legionellae and development of lung abscess. Legionellosis also is found in patients who have humoral immune defects, but to a lesser extent. Thus, multiple myeloma, chronic lymphocytic leukemia, and chronic granulomatous disease have all been complicated by Legionella infection, although the risk seems to be minimal.

A 44-year-old woman developed Legionella pneumophila pneumonia after cerebral surgery. Initially, one colony from a clinical specimen and two colonies from water samples, all belonging to serogroup 12, did not match when their DNA restriction patterns were compared. When additional colonies from the water specimens were analyzed, a serogroup 12 strain complementary to that found in the clinical specimen was identified. Other colonies from the clinical specimen were identified as serogroup 12 strains complementary to those identified from the water. In addition, the same serogroup 1 strain was isolated from the patient and the water system.

A 72-year-old man was exposed to the sarin gas attack in a Tokyo subway on March 20 th, 1995. After exposure, he noticed eye discomfort, chest tightness, headache and weakness of the lower limbs and oropharyngeal muscles. Despite these symptoms, he visited a hot spring on the same day with his family. On March 25 th, his muscle weakness progressed, and a low grade fever appeared. His muscle weakness disappeared 8 days after exposure to sarin, but respiratory failure rapidly developed, necessitating artificial ventilation within four day after hospitalization on March 28th. Chemotherapy with erythromycin, imipenem/cilastatin, and steroid pulse therapy was begu. PCR and culture of sputum collected by bronchofiberscopy were positive for Legionella pneumophila, serogroup I. His respiratory state improved, but subsequent infection with Pseudomonous aeruginosa. Enterobacter cloacae, and Candida tropicalis/glabrata caused his death 71 days after admission. Oropharyngeal muscle weakness caused by sarin-mediated cholinesterase inhibition was strongly suspected as the cause of hot spring water aspiration. Transbronchial lung biopsy revealed organizing pneumonia with fibrosis. Bronchoscopic findings included redness, edema and fragility of all visible areas of the airway, which was thought to be due to bronchitis caused by Legionellosis.

The clinical course of legionella pneumonia in immunosuppressed patients is uncertain. This study was undertaken to determine the clinical evolution of legionellosis on the basis of the immune state and to establish the variables associated with death directly related to legionellosis. The study included 78 patients: 28 with chronic disease who had received immunosuppressive treatment (group 1), 24 with chronic disease without immunosuppressive treatment (group 2), and 26 controls. Inclusion criteria were the occurrence of nosocomially acquired pneumonia, Legionella pneumophila infection, and erythromycin therapy that was initiated within 72 hours following diagnosis. Respiratory and extrarespiratory complications were observed more frequently in groups 1 and 2. Bilateral radiological involvement was most frequent in group 1, and recurrence of legionella pneumonia was observed exclusively in group 1. None of these variables achieved statistical significance. The global mortality of the series was 11.5% (17.9%, 12.5%, and 3.8% in groups 1, 2, and 3, respectively). Variables statistically related to mortality were acute renal failure, shock, and need for mechanical ventilation. Although many of the variables analyzed lacked statistical significance, a trend was seen between complications and basal immunosuppression, as previously suggested.

A case of community-acquired Legionnaires' disease (LD) is described. The source of infection was traced to a push-on tap at the end of a long spur from the hot circulation system in a large old residential building which had been unoccupied for several weeks. Legionella pneumophila serogroup 1 subgroup Pontiac was isolated from the patient's sputum and from the contaminated water supply. Isolates were shown to be indistinguishable from one another when subtyped by pulsed field gel electrophoresis of chromosomal DNA.

Two hundred and one cases of legionnaires' disease were reported to the PHLS Communicable Disease Surveillance Centre in 1996. Twenty-four cases (12%) were known to have died. One hundred and one cases were associated with travel, either abroad or in the United Kingdom. Two cases acquired infection in hospital, the smallest number ever reported, and the remaining 98 were presumed to have acquired infection in the community. Fifty-five (27%) of the 201 cases were linked to outbreaks or clusters and the remaining 146 (73%) were reported as single cases. Six outbreaks were associated with industrial premises. Twenty-two of the travel associated cases were part of three travel outbreaks and six clusters. The proportion of cases diagnosed by detection of urinary antigen has continued to increase and in 1996 this method of diagnosis was used for 43% of the cases.

Background: A community outbreak of atypical pneumonia occurred in summer 1994 in L'Espluga de Francolí, Tarragona, Spain, affecting 20 people., Patients and Methods: The clinical and epidemiologic description of the outbreak are performed, as well as the sanitary actions leading to the discovery of the original focus (an hotel refrigerating tower). Through case-control studies (among the 17 in-home contagions according to their nearness) and using the causality criteria of Evans and Bradford-Hill., Results: Although the symptomatical description brings forth new symptoms such as hyperglycemia or livedo reticularis, the comparative clinical-therapeutical study bears no significant differences with other series, and the radiological data as well as the response to the treatment are wholly overlapping, with results less coincident in those coming from the lab, very specially due to the small sensibility the indirect immuno-fluorescence showed., Conclusions: The epidemiologic study demonstrates the etiology of the outbreak (Legionella), their source in the refrigerating tower, in so much sterilization coincided with the end of the epidemy.

A 57-year-old male was admitted to our hospital because of high fever, productive cough and dyspnea. Six days prior to admission he had an episode of drowning in a public bath. On admission chest X-ray showed wide-spread pneumonia causing severe respiratory distress for which mechanical ventilatory support was started. Despite chemotherapy including erythromycin and rifampicin his condition continued to deteriorate. Chemistry showed marked elevation of CPK and findings of acute renal failure. He eventually passed away with septic shock. During the course Legionellae remained negative with culture of broncho-alveolar lavage fluid. L. pneumophila serogroup 1 (SG1) antigen in the urine was not detected, and no elevation of serum antibody titer was noted. Culture of the material obtained from the lung abscess at autopsy revealed L. pneumophila SG6 and serum antibody titer against SG6 also was found to be extremely high. With this evidence we concluded that this case of pneumonia was caused by L. pneumophila SG6. We believe this is the first reported case of the SG6 pneumonia in Japan. Another remarkable feature of this case was massive rhabdomyolysis pathologically confirmed after autopsy. Although the pathogenesis of this process has not been clarified, there are several case reports of rhabdomyolysis complicated with Legionnair's disease in the past. Therefore, we should bear in mind and pay careful attention while coping with this disease.

Contaminated whirlpool spas have been reported as a source of legionellosis. This report describes the preliminary findings of an ongoing investigation by the Virginia Department of Health (VDH) and CDC of a recent outbreak of Legionnaires disease in Virginia, which implicated a whirlpool spa display at a retail store as the source of infection.

Legionellosis is a contagious disease occurring either sporadically or more frequently in outbreaks, the infections being caused by members of the family Legionellaceae. The disease may show two clinical forms, i.e.: 1) the pneumonic form characterized by fever, pulmonary, neurologic and often hepatic and renal affections, severe evolution and high mortality rate; and 2) non-pneumonic form similar to influenza infection. Occurrence of the disease was mentioned almost all over the world its incidence in Europe reaching 1-3%. The infection sources are: warm water supply systems of hospitals, hotels etc.; water cooling towers, humidifier of air-conditioning systems, disperses for therapeutically applied aerosols, water sprinkling equipment, etc. Incubation period of the disease is 2-10 days. The factors favoring infection have to be looked for with all the conditions generating a decrease in activity of immunization system. Disease control steps through eliminating infection sources: water hyperchlorination, increase of water temperature in water supply systems at 60 degrees C for short periods, detachment of non-functional water pipes from the main trunk line. Occurrence of legionellosis is monitored by both active and passive means applied within the country and on an international level through the Reference Centres for Legionellosis.

The potential role of humoral immunity in regulating intrapulmonary growth of Legionella pneumophila in the immunocompetent host was investigated using a murine model of Legionnaires' disease. Intratracheal inoculation of A/J mice with a virulent strain of L. pneumophila (10(6) bacteria per mouse) resulted in the recruitment of B lymphocytes into the lung and the development of anti-L. pneumophila Ab. Opsonization of L. pneumophila in vitro with anti-L. pneumophila-specific mAb resulted in a significant decrease in intrapulmonary growth of the bacteria at 24 to 72 h postinfection. Transmission electron microscopic analysis of lung tissue from L. pneumophila- infected mice demonstrated that while there was no significant difference between phagocytosis of the unopsonized and opsonized L. pneumophila by alveolar macrophages at 24 h postinfection, phagocytosis of opsonized bacteria by alveolar mononuclear phagocytic cells was significantly enhanced at 48 h postinfection. Depletion of A/J mice of complement before intratracheal inoculation of opsonized L. pneumophila (10(6) bacteria per mouse) did not significantly alter intrapulmonary growth of L. pneumophila. These results suggest that anti-L. pneumophila Ab, produced during replicative L. pneumophila lung infections, may regulate intrapulmonary growth of L. pneumophila in the immunocompetent host by decreasing the viability of extracellular L. pneumophila and by enhancing phagocytosis of the bacteria by alveolar mononuclear phagocytic cells by a complement-independent mechanism.

Environmental monitoring and clinical surveillance for Legionella species were done for 12 months as recommended by the Allegheny County Health Department (Pittsburgh). The water system of a hospital was found to be colonized with Legionella pneumophila serogroup 5. Three patients with nosocomial L. pneumophila serogroup 5 disease were subsequently diagnosed after laboratory tests for legionellae were made available for all patients with nosocomial pneumonia. All serogroup 5 isolates from the hospital water matched the 3 patient isolates by pulsed-field gel electrophoresis (PFGE). Furthermore, isolates found in the water supply dating back 10 years showed the same PFGE pattern. In contrast, 12 L. pneumophila serogroup 5 isolates from eight other institutions had different PFGE patterns. Routine environmental cultures were important in stimulating the application of Legionella laboratory testing, which subsequently identified unsuspected patients with nosocomial legionnaires' disease.

Background: Legionnaires disease is a common cause of adult pneumonia. Outbreaks of legionnaires disease have been well described, but little is known about sporadically occurring legionnaires disease, which accounts for most infections. Exposure to contaminated residential water sources is I plausible means of disease acquisition., Methods: Employing a matched case-control study design in 15 hospitals in 2 Ohio counties, we prospectively enrolled 146 adults diagnosed as having nonepidemic, community-acquired legionnaires disease and compared each with 2 hospital-based control patients, matched for age, sex, and underlying illness category. An interview regarding potential exposures was followed by a home survey that included sampling residential sources for Legionella. Interview and home survey data were analyzed to estimate the risk of acquiring legionnaires disease associated with various exposures., Results: Multivariate analysis showed that a nonmunicipal water supply (odds ratio [OR], 2.26; 95% confidence interval [CI], 1.17-4.37), recent residential plumbing repair (OR, 2.39; 95% CI, 1.10-5.18), and smoking (OR, 3.48; 95% CI, 2.09-5.79) were independent risk factors for legionnaires disease. Univariate analysis suggested that electric (vs gas) water heaters (OR, 1.97; 95% CI, 1.10-3.52), working more than 40 hours weekly (OR, 2.13; 95% CI, 1.12-4.07), and spending nights away from home before illness (OR, 1.68; 95% CI, 1.03-2.74) were additional possible risk factors. Lower chlorine concentrations in potable water and lower water heater temperatures were associated with residential Legionella colonization., Conclusions: A proportion of sporadic cases of legionnaires disease may be residentially acquired and are associated with domestic potable water and disruptions in residential plumbing systems. Potential strategies to reduce legionnaires disease risk include consistent chlorination of potable water, increasing water heater temperatures, and limiting exposure to aerosols after domestic plumbing repairs.

The effect of inhaled amoebae on the pathogenesis of Legionnaires' disease was investigated in vivo. A/J mice, which are susceptible to replicative Legionella pneumophila infections, were inoculated intratracheally with L. pneumophila (10(6) bacteria per mouse) or were coinoculated with L. pneumophila (10(6) bacteria per mouse) and Hartmannella vermiformis (10(6) amoebae per mouse). The effect of coinoculation with H. vermiformis on bacterial clearance, histopathology, cellular recruitment into the lung, and intrapulmonary levels of cytokines including gamma interferon and tumor necrosis factor alpha was subsequently assessed. Coinoculation with H. vermiformis significantly enhanced intrapulmonary growth of L. pneumophila in A/J mice. Histopathologic and flow cytometric analysis of lung tissue demonstrated that while A/J mice inoculated with L. pneumophila alone develop multifocal pneumonitis which resolves with minimal mortality, mice coinoculated with H. vermiformis develop diffuse pneumonitis which is associated with diminished intrapulmonary recruitment of lymphocytes and mononuclear phagocytic cells and significant mortality. Furthermore, coinoculation of mice with H. vermiformis resulted in a fourfold enhancement in intrapulmonary levels of gamma interferon and tumor necrosis factor alpha compared with mice infected with L. pneumophila alone. The effect of H. vermiformis on intrapulmonary growth of L. pneumophila in a resistant host (i.e., BALB/c mice) was subsequently evaluated. While BALB/c mice do not develop replicative L. pneumophila infections following inoculation with L. pneumophila alone, there was an eightfold increase in intrapulmonary L. pneumophila in BALB/c mice coinoculated with H. vermiformis. These studies, demonstrating that intrapulmonary amoebae potentiate replicative L. pneumophila lung infection in both a susceptible and a resistant host, have significant implications with regard to the potential role of protozoa in the pathogenesis of pulmonary diseases due to inhaled pathogens and in the design of strategies to prevent and/or control legionellosis.

The cases of two elderly patients who complained of general malaise after they had undergone ward transfer (due to rationalisation of the rehabilitation service) are discussed. Both were pyrexial and had signs of pneumonic consolidation. Subsequent investigation revealed that their symptoms were due to infection with Legionella pneumophila. Their cases highlight the problems associated with ward closures and the hazards of stagnant water.

Pulmonary infections are a significant cause of morbidity after liver transplantation; Gram-negative bacilli, cytomegalovirus, and Pneumocystis carinii were the usual pulmonary pathogens in the earlier studies in liver transplant recipients receiving cyclosporine. We prospectively assessed the impact of pulmonary infection in 101 consecutive liver transplant recipients receiving the new immunosuppressive agent tacrolimus (FK506). Fifteen percent (15/101) of the patients had 19 episodes of pneumonia; 58% (11/19) of the pneumonias were bacterial, 37% (7/19) were fungal, and 5% (1/19) were protozoal (Toxoplasma gondii). Twenty-seven percent of the bacterial pneumonias were due to Legionella. None of the patients had cytomegalovirus or P carinii pneumonia. Seven percent (7/10) of the study patients had fungal pneumonitis; 4% had invasive aspergillosis and 3% had cryptococcosis. Mortality was significantly higher (53%, 8/15) for patients with pneumonia than for patients without pneumonia (10%, 9/86, P = 0.0004). Only fungal pneumonias were the direct cause of death; 63% (5/8) of the deaths were in patients with fungal pneumonitis. Our data suggest a changing pattern of microbial etiologies of pneumonitis in the era of modern immunosuppressive agents. We show that P carinii pneumonia and cytomegalovirus can be effectively curtailed with appropriate prophylaxis. Fungal infections, on the contrary, not only constituted a major proportion of the pneumonia, but also carried the highest pneumonia-associated mortality. Legionella infections can be overlooked unless specialized laboratory methodology (cultured on selective media, urinary antigen) are applied routinely on all cases of pneumonia. We recommend routine culture on the water supply for Legionella in all transplant centers.

Not all new threats from microorganisms result from changes within the microorganisms themselves. Innovative, progressive changes introduced by humans can provide advantages to microbes which, in turn, threaten the population. In most cases, advantages are provided unwittingly as a by-product of technology, and can be corrected when the problem is recognized. An end to progress is neither a practical nor desirable solution. Alertness (i.e., surveillance) for the emergence of new diseases and to changes in disease patterns will continue to be critical to ensure timely implementation of public health measures.

A 71-year-old Japanese female, was found unconscious by drawing, in a hot spring spa, at around noon of 20 October 1994. She recovered by emergency cardiopulmonary resuscitation, and admitted to the Takinomiya General Hospital, with adult respiratory distress syndrome (ARDS). Although she recovered from ARDS within 4 days after her admission, she developed severe pneumonia accompanied with the second attack of ARDS. Ordinary bacteriological culture of her respiratory specimens failed to yield any significant pathogen for her pneumonia, and neither cefazolin nor imipenem/cilastatin was effective. Thus minocyclin was given on the 7th hospital-day and this was effective for blood gas and C-reactive protein (CRP) levels. Intratracheal exsudate inoculated on BCYE alpha agar plate yielded grayish white colonies. Cells of the colonies were clearly agglutinated by anti-Legionella pneumophila serogroup (SG) 3 serum. Antibody titers of patient's paired sera against the strain L. pneumophila SG3 Bloomington-2 and the patient's strain (Y-1) were determined by microplate agglutination test, and a significant rise from 1:20 to 1:320 was demonstrated. Patient recovered by erythromycin treatment and was discharged on the 59th hospital day. L. pneumophila SG3 organisms were again isolated from the spa water where the patient drawn. From these findings described above, we diagnosed the patient as pneumonia due to L. pneumophila SG3, and the spa water was the most probable source of infection.

A lack of standardization of environmental monitoring techniques for Legionella spp. complicates the interpretation of results and comparisons of results from different institutions. A comparative assessment of techniques recommended by the Centers for Disease Control and Prevention, the Hygiene Institute (Graz, Austria), and our laboratory was performed. Variables investigated were sampling method (swabbing and collection of water samples [250 ml] before and after swabbing), method of concentration (none, filtration, and centrifugation), acid buffer treatment (no acid treatment, treatment for 3 min, and treatment for 15 min), and choice of medium (five formulations of buffered charcoal yeast extract agar with glycine, vancomycin, polymyxin B, anisomycin, or cycloheximide). Thirty-three sites in seven hospital buildings were studied. Recovery by swab correlated with recovery from water after swabbing (P < 0.05). However, the quantity of Legionella spp. recovered from swab specimens (mean, 3.0 x 10(4) CFU per swab) was greater than that recovered from water (mean, 4.7 x 10(3) CFU/250 ml). Filtration resulted in recovery rates (mean, 5.2 x 10(3) CFU/250 ml) higher than those by centrifugation (mean, 2.3 x 10(3) CFU/250 ml). Three minutes of acid buffer treatment to reduce overgrowth by commensal flora did not improve selectivity or sensitivity for Legionella spp. if glycine-containing selective media were used. Fifteen minutes of acid buffer treatment reduced recovery compared with that after a 3-min treatment. All glycine-containing media tested effectively inhibited background flora, but one selective medium containing dyes, glycine, vancomycin, and polymyxin B (DGVP) resulted in the greatest quantitative recovery of Legionella pneumophila. Use of buffered charcoal yeast extract agar and the acid buffer treatment gave the greatest recovery of non-pneumophila species. A standardized protocol with an emphasis on the culturing of swab samples is presented.

In order to understand the risk factors of legionella infection in children a case-control study with two kinds of controls was conducted. The stepwise regression analysis included age, sex, season and immunosuppressive therapy in regression equation. The non-conditional logistic regression analysis showed that age, passive smoking and touching soil were associated with legionella infection. The statistics analysis also showed that there were dose-response relationship between age, passive smoking and immunosuppressive therapy and the frequency of legionella infection in children. It was suggested that age, season, immunosuppressive therapy, passive smoking and touching soil were risk factors for legionella infection.

Objective: To describe two cases of nosocomial legionellosis and discuss the epidemiology of this infection., Design: Potable water was collected from multiple sites. Patient and environmental isolates were characterized by the Legionella slide agglutination test and monoclonal antibody subtyping. Concordance among isolates was confirmed by pulsed-field gel electrophoresis (PFGE)., Setting: A 713-bed university-affiliated hospital., Results: There was widespread contamination of potable water with Legionella pneumophila during a period of major construction; cooling towers were without growth of Legionella. One patient's isolate was the same by PFGE as the environmental isolate collected from the water faucet in his room. Control measures included superheating water used in all patient care areas to 75 degrees C for 72 hours and flushing superheated water through faucets and showers; cleaning shower heads with a sonicator washer; and raising the hot water storage tank temperature from 43 degrees C to 52 degrees C. After these interventions, repeat environmental cultures over the next 6 months were without growth of Legionella, and no further cases of nosocomial legionnaires' disease were documented. An association between legionnaires' disease and construction is postulated. Heightened surveillance and preventive measures may be warranted during periods of excavation on hospital grounds or when potable water supplies are otherwise shut down and later repressurized.

Asthma is increasingly treated as an inflammatory disease with inhaled and/or systemic corticosteroids. We report 3 cases of unusual pneumonias associated with high doses of oral steroids. Two patients contracted Legionella pneumonia and one patient contracted Pneumocystis carinii pneumonia. With increasing usage, it is important for physicians to be aware of the possible infectious complications of high dose steroids. This report highlights the risk of corticosteroid treatment in asthma in predisposing to opportunistic infections that have not heretofore been readily associated with asthma.

Problem: Two cases of nosocomial legionellosis due to Legionella pneumophila serogroup 6 (Lp6) were identified in the intensive care unit. Both patients had a history of aspiration of nasogastric tube feedings, developed pulmonary infiltrates, had positive cultures for Lp6, had serological titer rises to Legionella, were treated, and recovered., Method: Isolates of Lp6 from the potable water system and patients were characterized by DNA restriction enzyme analyses using pulsed-field gel electrophoresis (PFGE)., Results: Water samples grew > 10(4) CFU/L of Lp6, and the same PFGE pattern was observed with the patient and water isolates. Potable water was used only for delivering medications and diluting feeding solutions given through the nasogastric tubes of the patients. Heat shock of the hot water system (140 degrees to 160 degrees F or 60 degrees to 70 degrees C, 4 hours) was performed and the temperature was maintained between 131 degrees to 140 degrees F (55 degrees to 60 degrees C). Surveillance over 18 months revealed a reduction in Legionella to < 10(2) CFU/L., Conclusion: We speculate that nosocomial Legionella pneumonia occurred due to aspiration of nasogastric tube solutions diluted with tap water. A nursing practice change to use only sterile water to dilute feedings and flush medications for nasogastric administration was instituted. The hot water temperature at the faucet was increased to > or = 131 degrees F (> or = 60 degrees C) to control Legionella. No further nosocomial cases have occurred.

From July through October 1993, outbreaks of Legionnaires' disease (LD) were reported from communities in Massachusetts and Rhode Island and from a state prison in Michigan. Cooling towers (CTs) were identified as the source of all three outbreaks. This report summarizes investigations by state and local health officials and CDC and efforts to control these outbreaks.

To determine the effects, if any, of the Zn-metalloprotease on virulence of Legionella pneumophila infection, an isogenic mutant deficient in protease (encoded by the proA gene) was tested in an Acanthamoeba cell model, in guinea-pig macrophages, and in a guinea-pig pneumonia model. The cloned proA gene was completely inactivated by insertion of a kanamycin-resistance cassette into the protease gene of L. pneumophila AA100. This mutated gene was then introduced into the L. pneumophila chromosome by allelic exchange to form the isogenic ProA- mutant AA200. AA200 showed no difference in its ability to enter, survive, or grow in Acanthamoeba and explanted guinea-pig macrophages; neither light nor electron microscopy revealed morphological differences in the eukaryotic cells infected with the protease mutant or the wild-type strains. The proA gene was found to be expressed in L. pneumophila during intracellular growth in amoebae by measuring the light produced from a truncated luxC gene fusion with the proA promoter. Virulence of the protease mutant was attenuated when tested in a guinea-pig model of infection employing the intratracheal inoculation method. AA200 was slower to cause death, grew to lower numbers in the lungs, resulted in less necrotic debris and a larger macrophage infiltrate, and was more likely to be found in association with macrophage vacuoles than the parent strain. Although deletion of the protease was not sufficient to completely abolish virulence in a guinea-pig model, the mutation caused a delay in the lethal effects of L. pneumophila and attenuated the infection.

The investigation, epidemiology, and effectiveness of control procedures during an outbreak of Legionnaires' disease involving three immunosuppressed patients are described. The source of infection appeared to be a network of fire hydrant spurs connected directly to the incoming hospital mains water supply. Removal of these hydrants considerably reduced, but failed to eliminate, contamination of water storage facilities. As an emergency control procedure the incoming mains water was chlorinated continuously. Additional modifications to improve temperature regulation and reduce stagnation also failed to eliminate the legionellae. A perspex test-rig was constructed to model the pre-existing hospital water supply and storage system. This showed that through the hydraulic mechanism known as 'temperature buoyancy', contaminated water could be efficiently and quickly exchanged between a stagnant spur pipe and its mains supply. Contamination of hospital storage tanks from such sources has not previously been considered a risk factor for Legionnaires' disease. We recommend that hospital water storage tanks are supplied by a dedicated mains pipe without spurs.

Two hundred and eighteen nosocomial cases of Legionnaires' disease with 68 deaths were reported to the National Surveillance Scheme for Legionnaires Disease between 1980 and 1992, representing 15% of the reported infections acquired in England and Wales. Twenty-two nosocomial outbreaks accounted for 135 (62%) of these cases, the remainder occurring as single cases either in hospitals where other single cases or outbreaks had been reported in different years or as 'sporadic' cases in hospitals from which no other cases were reported. A clinical history prior to onset of Legionnaires' disease was available for 124 patients, 61 of whom had undergone recent transplant therapy or were immunosuppressed for other reasons. Sixty cases (27%) were diagnosed by culture of the organism and isolates from 56 patients were typed; 25 (42%) were non L. pneumophila serogroup 1 infections. Methods for prevention and control of nosocomial outbreaks are discussed, in particular the susceptibility to Legionnaires' disease of certain groups of hospital patients.

Over a 5-yr period, from January 1985 to January 1990, we prospectively studied 300 episodes of nosocomial pneumonia in a 1,000-bed teaching hospital. All cases had an accurate bacteriologic diagnosis obtained by means of highly reliable techniques. Legionella pneumophila caused a total of 36 episodes; 22 were endemic and 14 occurred during an epidemic outbreak. No patient with Legionella pneumonia had been intubated before infection. To identify risk factors for nosocomial L. pneumophila pneumonia, we compared the 22 endemic cases of nosocomial pneumonia due to L. pneumophila with the 264 cases due to other bacteria. After adjusting for other variables by means of logistic regression analysis, cytotoxic chemotherapy (OR = 5.2; 95% CI, 1.5 to 17.9) and use of corticosteroids (OR = 4.6; 95% CI, 1.5 to 14.1) were positively associated with L. pneumophila pneumonia, whereas previous antibiotic therapy (OR = 0.2; 95% CI, 0.1 to 0.8) and lowered consciousness (OR = 0.2; 95% CI, 0.07 to 0.8) were negatively associated. The major risk factors for Legionella pneumonia delineated in this study should be considered in the clinical approach to and empiric therapy of patients with suspected nosocomial pneumonia.

Legionella pneumophila was mutagenized with Tn903dIIlacZ, and a collection of mutants was screened for defects in macrophage killing (Mak-). Of 4,564 independently derived mutants, 55 (1.2%) showed a reduced or complete lack in the ability to kill HL-60-derived human macrophages. Forty-nine of the Mak- mutants could be assigned to one of 16 DNA hybridization groups. Only one group (9 of the 10 members) could be complemented for macrophage killing by a DNA fragment containing icm and dot, two recently described L. pneumophila loci that are required for macrophage killing. Phenotypic analysis showed that none of the mutants were any more sensitive than the wild type to human serum, oxidants, iron chelators, or lipophilic reagents nor did they require additional nutrients for growth. The only obvious difference between the Mak-mutants and wild-type L. pneumophila was that almost all of the Mak- mutants were resistant to NaCl. The effects of LiCl paralleled the effects of NaCl but were less pronounced. Resistance to salt and the inability to kill human macrophages are linked since both phenotypes appeared when Tn903dIIlacZ mutations from two Mak- strains were transferred to wild-type backgrounds. However, salt sensitivity is not a requisite for killing macrophages since a group of Mak- mutants containing a plasmid that restored macrophage killing remained resistant to NaCl. Mak- mutants from groups I through IX associated with HL-60 cells similarly to wild-type L. pneumophila. However, like the intracellular-multiplication-defective (icm) mutant 25D, the Mak- mutants were unable to multiply within macrophages. Thus, the ability of L. pneumophila to kill macrophages seems to be determined by many genetic loci, almost all of which are associated with sensitivity to NaCl.